1. Field of Invention
This invention relates to a variable speed integrated motor assembly for use in applications where precise and variable speed capability is essential.
2. Description of Prior Art
DC motors made their introduction into disk drives in the early 1980""s replacing the more larger and complex AC motors and controllers with a smaller, lower power, and more cost-effective assembly. Stator coils are hand or machine wound and then arranged in a circumferential pattern around the rotors permanent magnets. To sense rotor position during operation, multiple Hall probe type sensors, were placed in the stator assembly, that sense the magnetic field intensity in the motors air gap. To eliminate the cost of the Hall probes a sensor-less type control was implemented using the back EMF generated by the coils to determine motor speed. The output of either the Hall probes or the back EMF is used by complex external control circuits that applies current to the stator coils to regulate motor speed and direction.
This multi-part design is complex, expensive and requires several vendors to implement the design, i.e., wound stator coils, Hall probe sensors and the electronic control circuit usually implemented as an integrated circuit (IC). This leads to complex packaging solutions, that are specific to the application, and involves extensive cabling and interconnections. In addition, the design and implementation is not easily extended to the markets requiring multi-speed operation.
Accordingly, several objects and advantages of my invention are:
To provide a parallel rotor-stator assembly, separated by a small and precise air gap, thus increasing the magnetic flux density (and Torque) in the air gap.
To provide an integrated stator assembly that includes the stator coils, magnetic field sensors and control electronics IC.
To provide a permanent magnet rotor assembly with a low reluctance magnetic return.
To provide a variable speed motor that can change speeds rapidly on command from a host system.
Further objects and advantages of my invention will become apparent from a consideration of the drawings and ensuing description.